1. Field of the Invention
This invention pertains to remote reading, liquid parameter measuring devices, particularly liquid levels in a reservoir, and to an air pump for use in this and other devices. More particularly, the invention is directed to a remote reading measuring device which contains a supply of gauge liquid that cannot leak from the device during shipment or in use.
2. Description of the Prior Art
Remote reading, liquid level measurement devices have been employed for many years. U.S. Pat. Nos. 2,012,511; 3,834,236 and 2,653,477 disclose structures which are intended to be permanently mounted in a location remote from the container having the liquid level to be measured. Generally, these devices are air-powered; that is, a pump provides a quantity of air to a tube immersed in the liquid to be measured and also to a manometric readout tube so that by supplying enough air to bubble out through the liquid to be measured, a readout of the level in the container is obtained on the sight tube of the manometric readout. When the specific gravity of the gauge fluid in the manometric tube is known and the height of the liquid level in the container above the bottom of the tube is known, specific gravity can also be determined.
There are several difficulties with the patented known measuring devices. Suitable provision is lacking for loss of the gauge fluid within the measuring device. Thus most of the prior art measuring devices are to be permanently mounted in a fixed, upright position so as to maintain both accuracy of reading and prevention of loss of the gauge liquid.
U.S. Pat. No. 3,307,397 is a more portable type of liquid level indicator which is intended to be secured to the dashboard of a vehicle. In this device, however, again no provision is adequately made for loss of the gauge liquid or errors when the angle of the device or, more specifically, the angle of the manometric sight tube in the device becomes too great so as to produce grossly inaccurate readings on the sight tube.
Another feature of the invention is directed to the problem that the manual pressurizing pumps for the prior art devices have involved expensive diaphragm pumps and check valves to provide the necessary pressurized air and venting, as is required for a manometric device.
Another feature of the invention is directed to the problem that none of the prior devices have an accurate, easy-to-follow technique for placing the tube within the liquid to be measured at an accurate distance below the level of the liquid in the container so as to accurately calibrate the sight tube in the manometric measuring device.